I have made a pcb with DB25 connector for BOB and a print for stopping starting spindle. Software used GRBL1.1 and UGCS

this is how the nano is connected
Attachment 469362

Attachment 469364

the print with nano
Attachment 469366

Attachment 469368

connections BOB
Attachment 469370

schematic BOB (maybe some errors ??)
Attachment 469372

pcb start stop with relay
the start stop is in GRBL done with the pmw ( 0-10V) signal.
GRBL uses pin D11 for start/stop and rpm control.
the voltage have to be above 1 V to start the spindle. Just use S and M3 /M5
Attachment 469374

this is how the drivers are connected
Attachment 469376

Here I have to stop because I am on my limit for 8 files.